Fix sending log messages from GPU child threads
Fix sending log messages from GPU child threads

This fixes a problem with sending log messages from children threads of the GPU
process. In GPU process the message goes through GpuProcessLogMessageHandler()
and to ChildThread::Send(), but there it would fail on
DCHECK(MessageLoop::current() == message_loop()), try to output another
log message about it, and since the handler is overriden, it would go back to
GpuProcessLogMessageHandler, and back again to ChildThread::Send() and thus
recurse until eventually dying silently due to stack overflow.

BUG=
TEST=manual run of a GPU child thread


Review URL: http://codereview.chromium.org/9812022

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@133824 0039d316-1c4b-4281-b951-d872f2087c98

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